Update: Two steps forward and one step back.
Thanks for all the comments and suggestions. For those suggesting a leak down test - I agree. But I haven't yet gotten my hands on the equipment to do that. For those suggesting I deal with the rich condition - I agree. I'll start that after I deal with the noise from cylinder 8. Here's what happened today.
I buttoned up the engine and ran it for 30 seconds or so to burn out the
oil in cylinder 8. Other than a cloud of smoke coming from the driver's side exhaust, it ran normally. I then pulled all the plugs and repeated the compression test. Cylinder 8 showed a good 210 PSI with the
oil gone. I drained and changed the
oil and oil filter. The old oil looked normal and there were only the usual fine iron filings on the magnetic drain plugs. With the plugs replaced, I ran the engine at idle until the water temp came up and all seemed normal. I then increased the RPM slowly to see if either the noise or KNOCK ALERT light would appear. Everything was alright until I reached about 3,500 RPM. At that point, a lot of smoke began to come from the driver's side exhaust and I shut it down.
An optimist would say the smoke was merely residual oil from the cylinder 8 test that had made its way into the exhaust and had finally gotten hot enough to produce smoke. A pessimist would say I had not found the root cause of the problem and it reappeared when the RPM got high enough. I say I've got too much to do for the next few days to deal with it now. I'll check it out the first of next week and see what I find.
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